1. Field of the Invention
The present invention relates to telephone network interface apparatus and to modular devices for interconnecting telephone company ("telco") wiring and subscriber telephone wiring. In particular, the invention relates to a modular device having a replaceable protection unit with overvoltage protection and/or transient protection and a replaceable electronics unit with a maintenance termination unit and/or a half ringer. The protection and electronics units may be integrated to form a single replaceable protection/electronics unit. The modular device may also have a plug-actuated switchable socket or a switch connected to an external socket for providing a point of demarcation between the telco wiring and the subscriber wiring such that an operating telephone can be plugged into the socket to determine whether a fault exists in the telco equipment or the subscriber premises. In addition, the modular device may have tool-less wire termination mechanisms for terminating and unterminating the telco and subscriber wiring at the modular network interface device without the use of tools.
2. Discussion of Related Art
Telephone subscribers may purchase and install their own telephone equipment and related appliances. Those subscribers are responsible for the proper operation of their equipment and the telephone company is responsible for service only up to the juncture between the telco wiring and the subscriber wiring. Thus, it is desirable to provide a telephone network interface apparatus which allows connection and disconnection of subscriber wiring from telco wiring so that the subscriber can readily isolate problems to the telco or subscriber equipment.
Modular devices are now available for use in telephone network interface apparatus that permit connecting and disconnecting the subscriber and telco wiring. Typical in the art are the modular devices shown in U.S. Pat. No. 4,979,209 issued to Thomas J. Collins et al. on Dec. 18, 1990, U.S. Pat. No. 5,153,910 issued to N. Peter Mickelson et al. on Oct. 6, 1992, U.S. Pat. No. 5,291,553 issued to Thomas J. Smith on Mar. 1, 1994 and U.S. Pat. No. 5,297,199 issued to Thomas G. Graham et al. on Mar. 22, 1994. There remains, however, a need in the art for easily installable modular devices having low cost and maintenance and increased functionality and reliability.
The Collins et al., Mickelson et al. and Graham et al. patents disclose modular devices having an RJ-11 telephone plug connected to the subscriber wiring and an RJ-11 telephone socket connected to the telco wiring to form a series electrical connection between the telco and subscriber wiring. When the plug is removed from the socket, the subscriber wires are disconnected from the telco wires and the subscriber may plug an operating telephone into the socket to determine whether a fault exists with the telco or subscriber equipment. The Mickelson et al. patent discloses a protective element and a test circuit as permanent parts of the modular device. The Collins et al. and Graham et al. patents disclose an internal space in the modular device for a telephone circuit. The Collins et al. patent further discloses overvoltage protection devices separate from the modular devices. The Collins et al., Mickelson et al. and Graham et al. patents disclose connecting the subscriber wires and the telco wires using screws and/or nuts.
The Smith patent discloses a modular device with a special, normally conducting RJ-11 socket to connect the telco and subscriber wiring. This special socket is also disclosed in U.S. Pat. No. 5,030,123 issued to C. Kevin Silver on Jul. 9, 1991. When a telephone is plugged into the socket, the subscriber lines are disconnected from the telco lines and the telephone is connected to the telco lines through the contacts in the socket. As an alternative embodiment, the Smith patent discloses a conventional RJ-11 socket and a conductive cap member to complete the circuit between the telco and subscriber wiring. When the cap member is removed from the socket, the subscriber wires are disconnected from the telco wires and a telephone can be plugged into the socket to determine the location of the fault. The Smith patent further discloses an overvoltage protection device and a specific terminating impedance for the telco wires as a permanent part of the modular device. Finally, the Smith patent discloses connecting the subscriber wires to terminals using screws and connecting the telco wires to terminals using nuts.
The prior art also discloses that telco and subscriber wires may be terminated using insulation displacement contacts. U.S. Pat. No. 5,153,911 issued to Thomas J. Smith on Oct. 6, 1992 discloses a weatherproof telephone terminal apparatus which employs a bolt which is turned to drive two mating parts together to force wires into slots in the insulation displacement contacts. U.S. Pat. No. 4,988,311 issued to Charles Tanzola on Jan. 9, 1991 shows a similar termination method. U.S. Pat. No. 5,273,449 issued to John S. Mattis et al. on Dec. 28, 1993 shows a method for attaching telephone "drop wires" to a plug in which wires are inserted into the plug and a cover is snapped shut, driving the wires into slots in the insulation displacement contacts. The Mattis et al. patent also discloses using a reenterable gel material in connection with the insulation displacement contacts.
U.S. Pat. No. 5,235,638 issued to Paul C. Dondero on Aug. 10, 1993 discloses a telephone network interface apparatus having separate telco and subscriber compartments. The subscriber compartment contains sets of modular devices while the telco compartment has sockets for receiving plug-in overvoltage protection modules and plug-in electronics modules which form side-by-side protector and electronics fields. U.S. Pat. No. 5,025,345 issued to Robert J. Marks on Jun. 18, 1991 discloses an overvoltage protection module with an integral 5-pin plug for use in a protection field. U.S. Pat. No. 5,175,662 issued to George A. DeBalko et al. on Dec. 29, 1992 discloses a module with an integral 5-pin plug which includes both overvoltage protection and a maintenance termination unit. U.S. Pat. No. 5,260,994 issued to Lou Suffi on Nov. 9, 1993 discloses a modular maintenance termination unit with a 5-pin plug which contains, as part of the module, a telephone socket and a telephone plug.
Finally, U.S. Pat. No. 1,303,383 issued to Ralph W. Osborne on May 13, 1919 and U.S. Pat. No. 4,433,212 issued to Donald W. Moses et al. on Feb. 21, 1984 disclose the use of inductances in series with telco lines.